The present invention relates to a support structure for a vibrating unit including a cantilever of a phono pickup cartridge.
In the prior art phono pickup cartridges, a support structure for supporting a vibrating unit, for example, in an MC type pickup cartridge, was constructed with an armature formed of a magnetic core with a coil wound therearound provided at a rear end of a cantilever. A suspension wire is provided along an extension of an axis of the cantilever, and the suspension wire is held and secured in a wire holder by adhesive, welding, or the like. The holder is then inserted into a hole formed in a pole piece which forms part of a magnetic circuit and is secured thereto by a screw or the like after adjustment of a damper pressure. The assembled units are mounted in a cartridge case by a resin filling or the like which, in turn, is mounted to a pickup arm.
FIG. 1 is a fragmentary perspective view of a prior art cartridge in which a pair of pole pieces 2 and 3 are mounted clamping a magnet 1. An armature 6 on which a coil is wound is secured to a rear end of a cantilever having at the other end a stylus 5. The cantilever 4 is secured to the rear pole piece 3 by a screw 7 through a wire holder and a suspension wire, a front end of which is coupled to the rear end of the cantilever 4. The magnetic unit, composed of the magnet 1 and pole pieces 2 and 3, supporting the vibrating unit including the cantilever 4 and the armature 6 is secured in a cartridge case 9 by synthetic resin. The cartridge case portion A is then connected to a pickup arm.
In such a construction, since the vibrating unit is pressed in one direction by a screw 7 and is secured through the suspension wire and the wire holder, there is a high probability that the overall vibrating unit when it is mounted will be offset from the center of the pole piece gap. Also, since the vibrating unit is secured by a single screw, the wire holder may have an inherent resonance. Furthermore, since the vibrating unit is supported with a synthetic resin which inherently has some compliance, an undesired resonance and accompanying degradation of sound quality inevitably result.